1. Field of the Invention
This invention relates generally to an apparatus for and a method of cooking fruit and the like products, and more particularly to such a cooking apparatus and method which employs steam as a heat exchange medium and as an agitating agent.
2. Prior Art
Steam has been employed extensively for heating and cooking various products. Steam has also been employed in the past for cooking fruit and similar products, such as dates, figs and prunes, for the purpose of liberating the sugar content of such products. The cooking process softens the fruit until it ruptures and exposes the pulp of the fruit to boiling or hot water, thereby liberating, over a predetermined cooking time, the sugar content of the fruit to the water. The resultant homogeneous mixture is refined and dehydrated to a desired fixed level for various commercial purposes. Examples of cooking apparatus which employ steam as a heat exchange medium are found in U.S. Pat. Nos. 1,174,721; 2,885,294; 1,565,282; 474,009; 1,711,729; 1,539,309; 2,020,309; 2,143,903; 2,589,288; 2,654,734; 3,374,096; 3,224,881; 3,764,708; Re.19,868; 3,139,345; and 1,955,289.
Previous methods of cooking fruit and the like products with the steam as the heat exchange medium have been either excessively expensive because of fuel costs or exceedingly slow. In order to obtain a high volume of production, such products must be cooked at the boiling point of water under turbulent conditions for short periods of time. If the cooking time is enlarged, it is likely that the products being cooked will be scorched, thereby effecting the flavor of the finished product. Although this method of cooking fruit produces a relatively high volume production, it requires and consumes relatively large amounts of fuel.
In the cooking of fruit and the like products, the heat may be applied as live steam in direct contact with the products or may be applied indirectly through a heat exchanger. Such indirect heating methods include, for example, the use of closed steam coils, heating compartments in the bottom of a tank, or jacketed tanks. Closed steam coils and jacketed type cooking chambers have distinct disadvantages in that the coil or jacket tends to collect and burn the products being cooked on the heated surface thereof. Furthermore, such devices contribute very little to the agitation that is required to rupture the fruit and expose its pulp to the boiling or hot water in which it is submerged. Accordingly, such devices require mechanical means for producing agitation of the product slurry. Such mechanical agitation is generally unsuccessful due to the presence of a foreign material and pits generally found in raw fruit which material may cause damage to the agitation elements.
By applying live steam which passes through the water in which the products are submerged and by maintaining such water at its boiling point, agitation is enhanced. The velocity of steam escaping from jets in a bottom portion of a cooking tank and the turbulence caused by boiling water generates sufficient agitation to aid in the rupture of the fruit to expose its pulp. This cooking method is capable of producing a relatively high yield in a relatively short time period. It also requires and consumes relatively large amounts of fuel, since a considerable amount of heat is lost by evaporation from the surface of the slurry. Moisture laden vapor or steam necessarily escapes from the surface of the slurry and is vented to the atmosphere, thereby creating a relatively large heat loss. This heat loss must, of course, be resupplied to the slurry to maintain its cooking temperature.